The Big Thompson flood of 1976 was the deadliest flash flood in Colorado’s recorded history. On July 31, between 12 and 14 inches of rain fell over a four-hour period in the mountains around the resort town of Estes Park. Unusual weather patterns allowed the huge storm system to stall over the area as it dumped its load.

Witnesses later described difficulty breathing in the moisture-laden air as the rain drove “straight down, lukewarm and not an ounce of wind,” creating a heavy spray all around them. Water gathered speed as it washed over the steep rocky hillsides and flushed through the flatter meadows, all of it heading for the bottom of the V-shaped canyon.

By 9 p.m., water sweeping into the Big Thompson River had taken it from an average depth of 18 inches to a 20-foot wall of water that crashed through the length of the canyon. Recordings taken at the mouth of the Big Thompson canyon showed the flow of water at 31,200 cubic feet per second at its peak.

Approximately 4,000 people were in the canyon during Colorado’s centennial weekend, most of them from outside the area. For some, the only alert of the danger was by word of mouth. Telephone lines were ripped and mangled – power poles and bridges destroyed. Huge boulders, trees, houses, propane tanks, cars, mobile homes and everything else in the path of the wall of water were tossed around as if in a giant blender. The frightening roar of the churning debris was illuminated by frequent lightning strikes.

State Patrol Sgt. W. Hugh Purdy left his Loveland home to investigate and support two of his officers who were called to the area on reports of rock slides. They quickly encountered a disaster in the making and tried to evacuate the area. Officer Purdy reported the dire rise of water levels as he neared the little town of Drake, but by then, he was trapped and overwhelmed by the rush of the flood. Other valiant police and fire officials made every effort to warn people and prompt them to take action.

Some of those who escaped did so with barely time to climb or drive out. Many who tried to drive out ahead of the storm were trapped in their cars and swept to their deaths.

The monstrous flood took 143 lives and injured 150 people. Some bodies were carried away as far as 25 miles. Some bodies were never recovered. One man who left the area that morning was presumed a victim until located decades later, living in Oklahoma. The flood caused $35 million in damage, destroying 418 homes and 52 businesses, 438 vehicles, bridges, roads, the highway and power and telephone lines.

In 2001, on the 25th anniversary, a stone memorial was placed near Drake, Colorado. The marker lists the names of those who perished in the flood.

One legacy of the historic event can be seen in the number of signs that now dot Colorado’s mountain roads and highways: “Climb to safety” in case of flooding.

1904: Floodwaters weakened a bridge near Pueblo, causing it to
collapse under the weight of a train, killing at least 97 people
and leaving 14 unaccounted for.

1921: The Arkansas River burst its banks after three days of rain.
Water roared through downtown Pueblo. More than 100 people were
presumed dead, though the death toll may have been higher because some
victims were transients and not easily traced.

1933: A dam on Cherry Creek failed after heavy rain. Seven people
died in Denver, and damage was estimated at $1 million. Also in 1933, a flash flood decimated Bear Creek Canyon, forever changing the little town of Starbuck, which is now known as Idledale. See more about this flood, with historic photos, here.

1965: Plum Creek and the South Platte River flooded through Denver,
killing 21 people and wiping out 2,500 homes and 750 businesses.
There was $540 million in damage, most of it uninsured.

1976: A flash flood through Big Thompson Canyon was the state’s
deadliest disaster, killing 144 people and causing $35.5 million in
damage.

1997: A flash flood in Fort Collins, killed five people and
caused $200 million in damage, including 25 buildings at Colorado
State University.